Line-Current Compensated Single Toroidal-Core Current Transformer for Three-Phase Current Measurement

A novel design of 100$\thinspace$: $\thinspace$1 single toroidal-core current transformer (CT) is described to measure line currents of a three-phase system. The toroidal core has three compensation windings associated with line conductors and a secondary winding. The current through a line conductor is measured, except the compensation winding of the sound phase, when the compensation windings of the other line conductors are active. The calibration and performance of the transformer are discussed for burdens 0.1 and 1 $\Omega$ over the current range 0–50 A. Test results indicate that maximum errors of measurements are comparable to the commercial CTs.